    H = [1.649,0.303;0.303,0.818]       % an arbitrary real symmetric matrix
    [U,D] = eig(H)                      % find eigenvectors  to diagonalize it
    H-U*D*U'                            % verification
    U*U'                                % verification
    p = [0.75,1.67]                     % some random vector
    q = H*p'                             % mulitply p by H
